Acute respiratory distress syndrome: a historical perspective

Abstract

Though well described even in ancient writings, the acute respiratory distress syndrome (ARDS) gained major medical attention with the availability of mechanical ventilation and establishment of intensive care units. In the 50 years since this beginning there have been remarkable advances in the understanding of the etiology, physiology, histology, and epidemiology of this often lethal complication of common human maladies. Until recently, improvements in outcome have mainly followed improvements in intensive care unit operation and their associated life support systems, and have not come through discoveries made in the course of prospective randomized trials. In spite of the remarkable increase in research focused on ARDS, there remain a large number of unanswered clinical questions that are potentially extremely important with regard to short-term morbidity as well as long-term outcome. The ARDS Clinical Trials Network study of tidal volume has proven that randomized trials in ARDS with positive results are possible even when using difficult primary outcome measures such as mortality or ventilator-free days. Therefore, the rich combination of new trial strategies, potential treatments, experienced investigators, and increasingly standardized routine care set the stage for rapid advances to be made in the short- and long-term outcomes of this devastating syndrome.

Figure 1.

Survival rates for ARDS have been increasing steadily as indicated from the reports of *Milberg, 1995 (51); ^†Weidemann – surfactant (56); ^‡ARDSNet – low tidal volume (55); and **ARDSNet – low PEEP (62).

Figure 2.

Several measures of long-term disability in surviving ARDS patients indicate slow and incomplete recovery. Data from Herridge, 2003 (67). Solid bars: forced vital capacity (% predicted); striped bars: 6-minute walk (% predicted); open bars: return to work (%).

Figure 3.

Venn diagram showing relative numbers of patients with acute respiratory failure (intubation and mechanical ventilation > 24 h), acute lung failure (ARF patients with Pa_O2/FI₀₂ > 300 mm Hg not explained by ventilatory failure), acute lung injury, and ARDS. Note that although ARDS makes up most of the population of ALI, ALI is a small fraction of the population with acute respiratory failure (see text definition). The total number of patients who would meet ALF criteria (i.e., abnormal oxygenation and bilateral infiltrates) is not known, but is substantially greater than the ALI population. (Adapted from Luhr and colleagues [124]).